The use of laser energy for therapeutic purposes has been proposed. Note, for example, an article entitled "Experimental Examinations on Laser Endoscopy" by Fruhmorgen et al, published in Endoscopy 6 (1974) at pages 116-122.
In the U.S. patent to Bass et al, U.S. Pat. No. 3,858,577, a flexible endoscope with a laser is described for performing laser surgery. The endoscope includes a sheath in which a plurality of optic fiber bundles are included. Another single optic fiber is provided to carry laser energy at a magnitude sufficient for therapeutic purposes.
In the U.S. patent to Bredemeier, U.S. Pat. No. 3,710,798 a laser system for microsurgery is described. A complex laser marking device is disclosed to indicate when the operating site is at the focal point of a converging operating laser beam.
Therapeutic employment of laser energy may involve laser light of different wavelengths. The argon laser, which is found to be particularly useful for blocking coagulation, produces energy in the visible spectrum. Observation of the impact point of a laser, when employed in an image transmitting endoscope, however, may result in an excessive, harmful exposure of the observer's eye.
When a laser or other radiation source is used whose energy is not in the visible region, care is needed to assure that high radiation energy cannot inadvertently become incident on the eye of an endoscope user. Such incidence is unlikely when the image transmitting path attenuates the laser beam. For example, the image transmitter may be a fiber optic bundle which is formed of a glass which attenuates the laser energy. There are, however, situations in which the attenuating fiber optic image bundle does not provide adequate attenuation such as in short endoscopes or when image transmitter paths with conventional optical elements are used.
When lasers or other high energy sources of invisible wavelengths are employed in an endoscope, care must be exercised that the emerging radiation beam impinges on the proper target of the body cavity. The targeting of a laser beam may involve a marking apparatus such as described in the Bredemeier patent. In an endoscope application, however, such marker is cumbersome and not conveniently suitable.